Modulation of static frequency changer current



1930. M. OSNOS 1,778,724

MODULATION OF STATIC FREQUENCY CHANGER CURRENT Filed Dec 2, 1925 ffie daaie frequency WI f f2 a l 5 0 F OZ ZZZMZZQ? INVENTOR MENDEL OSNOS A TORNEY Patented Oct. 2'1, i930 UNiTED STATES PATENT OFFICE MENDEL OSNOS, 0F BERLIN, GERMANY, ASSIGNOR TO'GESELLSCI-IAFT FllR DRAHTLOSE TELEGRAPHIE M. B. H., OF BERLIN, GERMANY, A CORPORATION OF GERMANY MODULATION OF STATIC FREQUENCY CHANGER CURRENT Application filed December 2, 1925, Serial No. 72,633, and in Germany December 4, 1924.

It is a well-known scheme in connection with the operation of high frequency installations comprising direct current excited static frequency changers, to modulate by means of varying the direct current excitation of the frequency doublers. However, in the practical application of this plan, a com paratively large change in the direct current excitation is necessary in order to eliminate the secondary voltage of double frequency; but the modulation of large variations of current cannot be taken care of with adequate rapidity, so that, as a general rule, especially in cases where high speed signalling is required, the direct keying method has been abandoned and special keying chokers are used.

N ow, according to the present invention the above is obviated by the aid of direct current excited static frequency doublers, The frequency is raised to a higher even harmonic, that is, it is multiplied in one stage by more than double (say, quadrupled, sextupled, and so on), while varying the direct current at the rhythm of the signalling or of the speech oscillations.

It will be noted that in this case, a very great variation of the useful voltage is accomplishable by the aid of comparatively small changes in the direct current magnetization. This follows, for instance, from the study by L. Dreyfuss published in Archiv fuer Eiektrotechnik, 1914, vol II, entitled The analytical theory of the static frequency doubler under no-load condition, especially from Figs. 18 to 20, according to which the generation of the maximum secondary voltage of double frequency, consid erably more direct current excitation is required than for the production or the maximum secondary voltage of a higher evenmultiple frequency, while for the elimina tion of the secondary voltages of a higher even frequency a by far smaller alteration of the direct current excitation is necessary than for the elimination of the secondary voltage of double frequency. l Vhence, it will be seen that the keying method which has not proved a success in the well-known keying of the frequency doubler, may advantageously be utilized in the production of 7 it changes in an inverse relation to the direct current.

The accompanying drawing by way of example illustrates a per se Well-known connection, in which a source of input energy, as the high frequency generator g through suitable tuning means delivers the-input energy of fundamental frequency to an Eppstein- Joly frequency changer T of known type, and whose output circuit or secondary windings s, and direct current windings f, are disposed differentially with reference to the primary windings pp. According to the invention, energy of higher even harmonic frequency, that is, of even, though more than double, frequency (say, quadruple, sextuple, etc.) is taken from the secondary winding, while keying is effected by means of key t in the circuit of winding f.

In the input circuit or generator circuit there may be arranged tuning means in well.- known manner consisting of capacities, inductances, or combination thereof, such as the series circuit W whose resultant impedance, including the impedance of the machine, shall be assumed to amount to XL ohms. Additional tuning elements, symbolized by the rectangle W may be connected in parallel at the terminals rat,- the resultant (capacitive or inductive) impedance of which is XG ohms. Now, if the tuning is to be so chosen that the primary current of the frequency changer does not change with change of the direct current, all that is necessary with this end in view (as can be seen from practical considerations) is to balance or adjust the tuning means in a Way so that XL together with XG results in resonance, in other words, that XL=XG. If the primary current is desired to change in inverse sense relative to the direct current, then XL and XG will have to be adjusted somewhat differently compared with one another in the one direction or in the other. Generally speaking, it will be lit necessary in practice to choose XG somewhat smaller than XL. Correct adjustment will be found by tentative tests and experimental tuning of the system. An additional series circuit may be connected in the frequency changer circuit, as is indicated at W By'the term modulation I mean alternating current control broadly, and "include telephony. and telegraphy modulation. By

theterm higher even harmonic I mean a harmonic'higher than double frequency, that is, say, a quadruple or a sextuple frequency. By the term input circuit, when referring to the tuning thereof, I include the reactance of the alternator or othersource of supply current. Having described my invention, What I claim is:' Y

7 1. A circuit for modulation comprising an input circuit for supply current, a saturable iron core, an output circuit for delivering modulated current, a direct current circuit for magnetizing the core, and means for varying the direct current to modulate the output current, the constants of the input circuit being so adjusted, relative to true resonance,

that upon variation'of the direct current the supply current does not vary or varies in inverse sense. i 7 i p 2. A circuit for frequency raising and modulation comprising an input circuit for current of fundamental frequency, a saturable iron "core, an output circuit for delivering current of a higher evenharmonic frequency, a d rect current c1rcuit for magnetlzing the core, and means for varying the direct current to modulate the output current, the input circuit being'so tuned, relative to true resonance for the fundamental frequency, that upon variation of the direct current the input current doesnot Vary or varies in inverse sense. i 1

3. Means for'frequen'cy'raising and modulat-ion comprising the combination With a frequency changer including an input circuit for current of fundamental frequency, a plurality of saturable iron cores, an output circuit for delivering-current .of'higher even harmonic frequency, and a direct current cir- .cuit for magnetizing the cores, said input,

output, and direct current circuits cooperatlng magnetically With said cores in suitable relation to obtain the desired harmonic frefundamental frequency that upon variation .quency, of means for varying the direct current to modulate the output current, the input circuit of said frequency changer being so tuned with respect to true resonance for the of thedirect current in either sense the input current does not vary or variesin the inverse MENDEL osNos.

sense. 

